🚀 go-pugleaf

In article <4ck70b$rd7@news.informix.com>, Daniel Wood <dwood> writes:
|> THE TEST CASE, on SCO:
|> 
|> main() { f(-2147483647, 1879048192); }
|> 
|> f(int x, int y) {
|> 	int r;
|> 
|> 	if ((r=(x-y)) > 0)
|> 		printf("1: r greater than 0\n");
|> 
|> 	if (r > 0)
|> 		printf("2: r greater than 0\n");
|> }
|> 
|> On SCO only the second print occurs.  The reason given to me is that ANSI
|> states
|> that the result of an overflowing/underflowing operation is undefined.  The
|> implementation is free to do what it wants with the result.  This is fine
<snip>
|> Saying a result is undefined "IS NOT EQUAL TO" saying that a C int
variable 
|> can actually hold an undefined value.  If you think the test case is
running 
|> acceptably, as described above, then tell me the section of the standard
that 
|> states or implies that an int variable can hold an undefined value.
|> 
|> Why say ye all?

3.14 defines `undefined behaviour' as `behaviour, upon use of nonportable or
erroneous program construct, of errnoeous data, or of indeterminately valued
objects, for which this International Standard imposes no requirements.' Note
that the entire _behaviour_ is undefined if erroneous data or an
indeterminately valued object is used. So, a compiler is within rights to do
whatever it sees fit, because it is not bound by any `requirements' of the
standard including, inter alia, the requirement that the value of a variable
not change arbitrarily; or that the controlled statement in an if be executed
if the control expressions evaluates unequal to 0.

Cheers
Tanmoy
-- 
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